Preliminary Design and Analysis of an Exhibition Centre in Hyde Park - Case Study Example

Preliminary design and analysis of an exhibition Centre in Hyde Park and ID number Preliminary design and analysis of an exhibition Centre in Hyde Park Section 1: Design Description Physical structures exhibit dynamic behaviour whenever subjected to loading or some form of displacement. Consequently, this calls for dynamic analysis of the structures, which is basically an extension of static analysis of structures. Real structures undergo infinite displacements and such analysis is not easy (Ahmet, 2007). This necessitates the use of computer models in simulation of the behaviour of the models. Computer model is a critical phase in structural analysis (Chen & Kareem, 2004). Such a model has a finite number of massless members and similarly, finite node number or rather joint displacements which sill help in simulation of the behaviour of the real structure. To accomplish appropriate understanding of dynamic behaviour of buildings, a single story building design is chosen. The computer model is for a building to be situated in North East area of Hyde Park, London is generated using SAP2000 and on basis of hand calculation complexities. The model developed in SAP2000 is a single story building. Despite London not being a nation associated with earthquakes, it still has an average rate of seismicity although not comparable to high seismicity areas such as California and Japan. Provided below is the floor plan of the building according to the design. Section 1.1 - Drawings The building as designed measures 144 by 72 by 14 feet and is a single story building. A plan view and two cross sections are provided to illustrate it appearance. Plan view Side view Sectional view Section 2 - Definition of model and calculations of loads Section 2.1 - Model assumptions Seismic weight at various floors: For the design, the design load is set to include a 25% minimum of live load. No live load is considered for the case of the roof. Consequently, the effective and functional weight is the loading which will be exerted (Buyukozturk, 2003). The effective roof weight will be 140 psf. The Plan area is 144 ft x 72ft = 10368 ft2. As a result, seismic weight = WG, 10368 x 0.17125 = 1775. Fundamental Period of Building: Where: = 0.030 (for the reinforcement concrete moment-resisting frame) = 14 ft (total building height) T = 0.030* 143/4 = 0.217 sec Occupancy Importance Factor: and similarly, Occupancy importance factor, Figure 1: London Spectra (Response Spectrum Curve) Mapped Response Spectral Acceleration: Short Period (T = 0.3 seconds) Ss = 3.046673g Long Period (T = 1 seconds) S1= 1.170548 g Co-efficient of the site = Fa = 1 SDS = 2.031115 Co-efficient of the site = Fv = 1 SD1 = 0.780365 Soil Modified Response Spectral Acceleration: SMS = Fa Ss = 3.047 SM1 = Fv S1 = 1.171 Design Response Spectral Acceleration: SDS = 2* 3.047/ 3 SDS = 2.031115 (Same as was is displayed in SAP 2000) SD1 = 2* 1.171 / 3 SD1 = 0.780365 (Same as was is displayed in SAP 2000) Response Modification Factor: R = 8 for Special Reinforced Concrete Moment Frame Seismic Design Category = D Seismic Coefficient: Cs = SDS*IE/R = 0.254 Check minimum value for Cs: Cs 0.044 * SD1 * IE = 0.03433606……………… Acceptable! Cs S1*0.5*IE/R = 0.073159……………………… Acceptable! Then Cs = 0.253889 Base Shear Force: V = Cs * W V= 0.253889 * 3012.4 V = 764.815 Kip Where: V = Seismic Shear of the Base. Cs = Seismic Coefficient of Response. W = Seismic structural weight of the structure which includes the dead weight and any other permanent loading including 25% of live load. Vertical Force Distribution: F = For, T = 0.56 seconds > 0.5 seconds K = 1.025 through interpolation Calculation of Seismic Lateral Force Level (ft) (Kip) (ft) (Kip-ft) (Kip) (Kip) (Kip-ft) 1 12 781.2 12.8 9975 80.187 764.81 17764.3 Section 2.2 - Applied loads Effect of loading is the prime focus for investigation and as such the load patterns, cases as well as combinations must be defined. To begin with, from the main menu, select “Define” and then the option “Load Patterns” are selected. Once done the option “Define Load Patterns” will appear with dead load as the default loading described. The other option “Live Load” must be imported as described. From the field “Load Pattern Name” the name Live is written while in the field “Type”, the “Live” option is selected from the resulting drop down menu. Value “1” is then input in the field indicated as “Self Weight Multiplier” after which the “Add New Load Pattern” pressed and conformed by pressing “OK”. The same procedure is replicated in adding wind load to the load patterns defined according to Eurocode. Section 2.3 - Wind load This is an advanced stage in analysis of the structure and loads are assigned to the frame as appropriate (Erol & Sashi, 2007). As had been earlier mentioned, loading takes various forms characteristically classified as dead and live loads. With regard to the dead load, Sap2000 is designed to automatically generate the loading effect based on the sections and the lengths made use of. Load is applied based on code conditions The wind load is assumed to act in a distributed pattern Wind load is presumed to act alongside the dead load Section 3 - Qualitative and approximate analysis Drift of the Story and its Lateral Displacement Strength as well as stiffness needs consideration of the special moment frames on the design. The special moment frames are to be designed for a force reduction factor provided as R = 8. This implies they are acceptable to design for a base shear which is equitable to an eighth of the value got from elastic response analysis. He frames are basically flexible lateral systems; consequently, strength necessities can be regulated by the minimum base shear equations relating to the applied code. The bases shear calculations relating to the long-period structures, have been evaluated and can regulate the special moment frame’s strength requirements. Stiffness Computation: = = 3600 Ksi = concrete modulus of elasticity = 12’-0” Exterior Column for First Story .1= 115.47 Kip/inch Interior Column for First Story .1= 200 Kip/inch Total Stiffness: = 18*115.47 + 9* 200 = 3878.46 Kip/inch Seismic Zone Factor: The seismic zone factor denoted as z is calculated by making reference to a Seismic zone map where London region falls in Zone 3, Description about dimensioning Floors: Floor Dimensioning: Rectangular plan 144’-0” x 72’-0”. Floor slab made use of in the structure is shell plate thin element having a thickness of 10 inches. When only the weight of the roof is acting on the building, a deflection similar to that of a simple beam is recorded; this is illustrated in the diagram below; Section 4 - Selected results of the design and analysis The total lateral forces of the design or design base shear (Vb) are obtained from SAP2000 with help of Response Spectrum Analysis as per Eurocode. The ordinates used are for medium soil for 5%damping. The design wind base shear (Vb) was calculated using procedures provided within the Eurocode as shown below, The capacity spectrum for building evaluated in the report is presented below The spectral acceleration coefficient (Sa/g) values for the given time periods ranging from 0.00 to 4.00 seconds calculated based on the equations given. Wind Load displacement Figure 2: 3D Wind displacement Earthquake output Figure 3: Earthquake 3D deformation A closer evaluation that an earthquake is likely to cause extensive damage on the building compared to wind whose effect is negligible. Nonetheless, none of the loading s considered completely destroys the building. Section 5 - Conclusions The aim of the study has been to perform an analysis of the structure of the steel building and observe its structural behaviour in the elastic range. Sap2000 offered a useful tool for linear and non-linear static and dynamic analysis and program’s design for 3 dimensional structures were made use of. Static and dynamic analysis was performed in order to understand the deformations, natural frequencies, as well as time periods. The model studies as mentioned at the reports onset was a simple structure building generated using Sap2000. The first phase of the project involved creation and analysis of the model and was later followed by analysis assuming medium soil condition. The three approaches including dead load only, wind load, and considering seismic effect. Response Spectrum analysis shows the model evaluated has a displacement within permissible limit for wind loading as provided for in the Eurocode standards while earthquake results into considerable deformation. References Ahmet, Y. (2007). Preliminary seismic performance assessment procedure for existing RC buildings. Engineering structures, 26, p. 1447-1461. Buyukozturk, O. (2003). Structural engineering design, Calculation of Wind and Earthquake Loads on Structures, ASCE 7 & IBC. Chen, X. & Kareem, A. (2004). Evaluation of equivalent static wind loads on buildings. J. Struct. Eng., 130, p. 1425-1435. Erol, K. & Sashi, K. K. (2007). Assessment of current nonlinear static procedures for seismic evaluation of buildings, Engineering structures, 29, p. 305-316. Read More